The invention relates to a method and apparatus for detecting the location of a marine pipeline or a cable.
Numerous pipelines (and cables) have already been placed during the last decades on and in the bottoms of seas and oceans, which pipelines have to be inspected from time to time, such as for checking the depth at which they are located below the sea or ocean bottom. Such inspection is carried out by vessels, such as surface vessels and submarines carrying equipment for detecting the presence of the pipeline (or cable) on or in the marine bottom for mapping the actual position thereof and at the same time taking other measurements in relation to the pipeline. Pipeline detection is usually carried out by generating a sequence of acoustic wave pulses by submarine wave transmitting means. Acoustic waves reflected by the pipeline are detected by submarine wave receiving means and displayed to show the position of the pipeline or cable with respect to the waterbottom.
In the prior art techniques, the wave reflections of the water bottom and the bottom layers, however, often obscure the wave reflections of the pipeline in the display of the records of the signals received by the receiving means, thereby rendering an accurate interpretation of the display impossible. The prior art techniques further have no means for indicating at which side of the vessel the pipeline is situated, and to obtain reliable information thereon, the vessel must be steered at a course that crosses the pipeline at a substantially right angle thereto. It will be appreciated that such crossings that have to be repeated many hundreds of times along the length of the pipeline, are a time consuming operation that renders the prior art techniques economically unattractive.